1. Field of the Invention
The present invention relates to non-reciprocal circuit elements, and particularly, to a non-reciprocal circuit element, such as an isolator and a circulator, for use in microwave bands, to a method for manufacturing the non-reciprocal circuit element, and to a communication device.
2. Description of the Related Art
Non-reciprocal circuit elements, such as isolators and circulators, have a characteristic that allows a signal to be transmitted only in a predetermined direction but not in the opposite direction. For example, by utilizing this characteristic, isolators can be used in transmitting circuits of mobile communication devices, such as automobile telephones and portable telephones.
Japanese Unexamined Patent Application Publication No. 2005-20195 (Patent Document 1) discloses a non-reciprocal circuit element, which is provided with a permanent magnet having outer peripheral dimensions that are greater than those of a center-electrode-attached ferrite so that a direct-current magnetic field is distributed uniformly over an entire region of the ferrite.
However, if non-reciprocal circuit elements of this type are to be manufactured by cutting out ferrite-magnet assemblies from a mother substrate, this manufacturing process is problematic in that it requires high costs. Specifically, the manufacturing process involves bonding individually manufactured center-electrode-attached ferrites accurately onto a permanent-magnet/mother substrate, and then cutting the workpiece into predetermined dimensions.